The general goal of the research is to study the mental operations involved in human intellectual behavior; studies on transitive reasoning by young children and language comprehension by adults are proposed. An information processing analysis of tasks is made using chronometric methods and stage description. Prior work has shown that subjects construct spatial representations in solving inference problems and that subprocesses such as coding, memory storage and retrival are critical. The proposed research is on non-spatial comparatives as well as tests of assumptions of the spatial model. Models for sentence verification are described and tested. Other linguistic work involves a test of semantic features and selection restrictions and aims at discovering how people learn meanings from sentences contexts.